Phalloplasty is the construction or reconstruction of a penis, or the artificial modification of the penis by surgery. Phalloplasty may involve taking a flap of tissue from a donor site to form a phallus. Phalloplasty may further include extending the urethra. Scrotoplasty can be performed using the labia majora (vulva) to form a scrotum where prosthetic testicles can be inserted. Phalloplasty may require an implanted prosthesis to achieve an erection. There are several types of penile prostheses, including malleable rod-like medical devices that allow the neo-penis to either stand up or hang down.